I think that would be a good option for a betta. Be sure to get a heater. I always hear that you should try and give your fish the most space possible. Here are some other options to consider, around the same price range:

I'm actually considering getting one of the 5 gallons I showed you for a betta tank as well. The Eclipse Corner 5 actually has an 11 watt compact flourescent bulb, which would give about 2.2 watts per gallon of light, if you're looking to grow aquatic plants too! It's what I'm leaning towards.

1. The filter flow is much too strong for a betta. You will need to reduce it but there are many ways to do this. While the pump is adjustable, the minimum flow rate would still whip the betta around in circles. You can cut holes into the pipe that leads from the pump to the output nozzle to reduce the flow.

2. The light that comes with the spec is good enough to grow low light plants as well. I think it turns out to be 8 watts or so with all those 32 LEDs. It is good enough for java fern, and Ièm guessing other plants such as hornewort, anubias, java moss etc. With the stock light I personally grew java fern, dwarf sage, and rotalla something (don't know which species exactly).

3. I think it is a bit too small for a betta. When I first got mine I was thinking about putting fish in there as well, but now that I have one oto in there alongside one red cherry shrimp I am thinking of making this a shrimp tank because it just doesn't seem big enough for the oto which is much smaller than a betta.

4. This is one expensive tank. Used 5g are much cheaper, and even brand new 5g kits are half the price of the fluval spec. If money is tight I would think twice before buying this.

5. The quality of this kit is really nice. The integrated filter system works fantastic, and it is really easy to hide a filter over the filter pump behind the back wall so it isn't seen.

So in the end it is your choice, I really like the spec, but my betta has his own 5g aquarium which I bought new but it still cost me less than the spec at half price.

__________________
10g Planted Tropical
1 male betta
4 cory cats

5g Planted Tropical
1 male Betta

Fluval Spec planted
1 male betta

Other pets
1 Russian tortoise
1 Pacman frog
All the pets at the petstore

My experience with smaller tanks = this...hard to keep up with the water changes in order to keep the fish 100% healthy lol.

I had my boy moonie in a 6.6 gallon tank with plants, I then got a great deal on sale at petco, 3 aqueon evolve 4 tanks, each holds about 2.5-3 gallons of water but in awkward shape! At first I loved them, all my bettas were equally housed and they looked really REALLY nice, like perfection. However, it didnt take long to get tired of doing 50% water changes every couple of days. My Plakat betta was miserable, spooked and jumped constantly (due to lack of space making him nervous), moonie started biting his tail leading to some fin rot issues (again due to lack of space) and my other betta No Nen who I recently rehomed started to develop fin rot. I used to stand by small tanks, loved them, for a while...After all is said and done, those evolve 4 tanks are sitting out on my back porch waiting for re-sale. I had to keep my 2 long tailed bettas in 1.5 gal hospital tanks to heal them up and again we ended up with Moonie chronically biting his tail.

I decided to count all my change and dollar bills and and ivest in 2 10 gallon tanks, best thing i could have ever done! Not joking. The tanks are soooo incredibly roomy, you could add some cory cats or ottos, snails and shrimp plus plants and decor. You can change the lights and opt for higher bulbs for plant growth. Both bettas are blowing bubble nests! this is a first for my plakat and Moonie hasnt blown a bubble nest since the first week I had him (ive had them both since august). I dont think ill ever go under 5 gallons with a betta again. Again this is all just my personal experience..now that im bitten by the big tank bug im a true follower lol.

Walmart has a good price for their 10 gallon kits, I paid in store $27.00..I did have to replace the filter (it was difficult to baffle the one it came with, but I keep it as an extra) and replaced the bulbs with zoomed 6500k 10watt bulbs, added a heater, sand, gravel, plants...probably total out $100 give or take a few. Well for me since I have 2 bettas, $200. You could probably get away with doing much cheaper than myself, I always go over board lol.
But with one betta id say $100 is reasonable all said and done.

I hope I didnt scare you away from getting a betta lol...they are seriously wonderful fish! And once you make the initially investment in setting it up correctly 1. you will be happy with the outcome 2. the cost will drop drastically as you'll need to buy things for upkeep (plant ferts, food, stress coat et, which I only buy every 2 months or so) 3. if uncycled - you will only need to do like 2 40% water changes a week (check tank perams incase you need to adjust it, but its so much easier!!!!) If the tank is cycled 1 50% each week will do.

They also have some nice 5 gallon kits out there! If you want plants though, steer clear of the LED 5 gal kit from walmart, those lights are way to small.

I really wish I never went with small tanks/bowls, I invested tons of money and time trying to make the smaller spaces betta friendly only to have them flop...now that ive upgraded tanks, life is much easier and way more relaxing, I can enjoy watching the fish more rather than worrying about them stressing out or constant water changes et.

I still cant decide on plant placement yet, I ended up puting them all in terracotta pots for now til I can decide but this is what it looked like when I had them in the substrate. He also has two nerite snails in his tank which he loves to pick on lol.
This is just to give you an idea of what you can do with 5-10 gallon tanks.

If you dont have the space for a larger tank, you can deffinitely make a a 1.5-4 gallon tank/bowl work, just heavily plant it with ammonia eating plants (hornwort or anacharis) and change the water often, like 50% 3x a week and somewhere in middle a 90-100% change.

Bettas are beautiful unique fish with very individual personalities and seem to really crave human interaction, its just purely awesome
Good luck with whatever you decide! Share pics!

If I could buy a 5-10 gallon tank I would but ..... I already have a Fluval EDGE ( with Guppies ans otocinclus) and my main concern is the space. I was looking for a tank that could sit on my desk. This is why I was thinking about buying a betta. They are so colorful. But the flow rate of the tank is also a problem. Any other idea about what type of fish ( no snails or crabs) I could but in the Fluval SPEC ??

The fluval spec really only can handle a few fish. I had the same question as you when I bought it about two months ago and I would recommend EITHER two otos OR 3-4 mosquito rasboras. My original plan was to do both, but after I had one oto die my plan is now to just add some shrimp and not try to squish any more fish in there. You could start a really nice colony of red cherry shrimp in the fluval spec. Thats my plan at least.

__________________
10g Planted Tropical
1 male betta
4 cory cats

5g Planted Tropical
1 male Betta

Fluval Spec planted
1 male betta

Other pets
1 Russian tortoise
1 Pacman frog
All the pets at the petstore

It's really not fit for a betta. The flow rate is too strong, and unless you are comfortable cutting up the pipe from the pump to the output to reduce flow I wouldn't add a betta. It is also tall and no very wide so it doesn't giva a lot of swimming space, but it's your choice if you want to house a betta in there, I just wouldn't.

__________________
10g Planted Tropical
1 male betta
4 cory cats

5g Planted Tropical
1 male Betta

Fluval Spec planted
1 male betta

Other pets
1 Russian tortoise
1 Pacman frog
All the pets at the petstore